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Method of manufacturing high strength dental restorations

Method of manufacturing high strength dental restorations description/claims

This application is a continuation-in-part of U.S. application Ser. No. 10/839,696, filed May 5, 2004, which claims priority to U.S. Application No. 60/468,935 filed May 8, 2003, all of which are hereby incorporated by reference.

The present invention relates generally to methods of manufacturing dental posts and more specifically to methods of manufacturing light curable fiber-reinforced polymeric composite dental posts

Light curable dental restorative materials are composite compositions of unsaturated functional monomers and fillers that are formulated to be polymerized by photochemical action upon exposure to light. The compositions will typically polymerize upon application of light in the 300-500 nanometer range. These composites have exhibited good mechanical properties after polymerization has been affected. Moreover, polymerizing the composites in inert atmospheres, under compressed air or in a vacuum has further enhanced the mechanical properties.

U.S. Pat. Nos. 6,320,162 and 6,236,020 to Friedman, which are hereby incorporated by reference, are directed to a method and apparatus for preheating single dose units of photocurable materials prior to clinical usage to enhance the properties of the composite. The patents describe the principal advantages of the preheating step as improved monomer conversion, improved material hardness, improved wear resistance, improved color stability, and improved strength. The inventor therein discovered that the reactive monomer in the photocurable material converted to a polymer in a substantially linear relationship over a temperature range from the refrigeration temperature of 20° F. to an elevated temperature of 150° F. Despite the advantages realized by this process, the inventor failed to note that by the time the photocurable material is delivered and shaped into a tooth cavity, the temperature of the material has cooled down to about 98° F. (body temperature). It is not much different than using an unheated photocurable material that will reach the temperature in the patient's mouth, i.e., 98° F., during insertion and before light curing. Moreover, the inventor cannot perform this procedure at temperatures higher than 150° F., since the procedure is being performed in a patient's mouth, and pulpal damage could begin to occur at that point. Therefore, the utilization of elevated temperature for a dental composite is minimal, and the benefit of such is limited.

Fiber-reinforced composite posts in the dental industry have exhibited adequate strength and light translucency, but have been deficient in radio-opacity. In order to increase the radio-opacity, it would be necessary to add more filler to the resin. The addition of more filler tends to increase the viscosity of the filled resin rendering it nearly impossible for penetration of the resin into the fibers.

Accordingly there remains a need to provide high strength fiber-reinforced composite posts having adequate strength and high radio-opacity. It would be beneficial to provide a facile and effective process for manufacturing high-strength and highly radiopaque fiber-reinforced composite posts.

The above-described drawbacks and disadvantages are alleviated by the method of the present invention for use with photo-initiated polymerizable dental compositions. The method comprises preheating a tooth restoration precursor of a defined shape or anatomy in a temperature range from about 65°-120° C. for a length of time for the temperature to reach a temperature equilibrium. The time preferably ranges from about 1 minute to 30 minutes, more preferably from about 1 to about 15 minutes and most preferably less than about ten minutes. Thereafter, the dental composition is light cured to polymerize the dental restoration. The restoration produced through this process will have at least 10% or higher strength than the dental restorations made by conventional methods.

In an alternate embodiment, fiber-reinforced composite posts are produced having high strength and high radiopacity. In a method of manufacturing the fiber-reinforced composite posts, fibers are polled through filled resin and heat is applied at various steps in the process to provide high strength and optimal radiopacity.

Features of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and wherein:

FIG. 1 is a perspective view of the manufacturing system of the present invention; and

FIG. 2 is a graph showing the effect of temperature on viscosity.

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